Known printing apparatuses, e.g., electrophotographic printers, execute a process designated as calibration to prevent degradation of image quality to result in printing due to environmental changes and consumption of components. In the calibration process, a toner image of a test pattern of each color is printed on a surface of an intermediate transfer belt, a position and toner density of the test pattern of each color are measured, and a color shift correction and a density adjustment are made for each color based on the measured results. The calibration process is executed automatically when it is determined that it is time to execute calibration, for example, after the expiration of a predetermined time interval from a previous calibration process.
The calibration process influences print quality during color printing more than during monochrome printing. However, if the calibration is started when print jobs are registered in a print queue, a monochrome print job, having a lower need for calibration when compared with a color print job, has to wait to start printing until after the calibration has been executed.